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Tag: Scarlett 2i2

One fact which I have written about before, is that I own a Scarlett Focusrite 2i2 USB-sound-device, and that I have tested whether it can be made to work on several platforms not considered standard, such as under Linux, with the JACK sound daemon, and under Android.

One conclusion which I can reach from this, is that the idea of setting my Linux software to a sample-rate of 192kHz, was simply a false memory. According to my own, earlier blog entry, I only noticed a top sample-rate of 96kHz at the time. And, my Android software only offered me a top sample-rate of 48kHz with this device.

The official specs state that its analog input frequency-response is a very high-quality version of 20Hz-20kHz, while its conversion is stated at 96kHz. What this implies is that when set to output audio at 44.1 or 48kHz, it must apply its own internal down-sampling, i.e. a digital low-pass filter, while at 88.2 or 96kHz, it must be applying the same analog filter, but not down-sampling its digital stream.

And so, whether we should be using it to record at 96kHz or at 48kHz, may depend on whether we think that our audio software will perform down-sampling using higher-quality filters than its internal processing does. But there can be an opposite point of view on that.

Just as some uses of computers see work offloaded from the main CPU, to external acceleration hardware, we could just as easily decide that the processing power built-in to this external sound device, can ease the workload on our CPU. After all, just because I got no buffer underruns during a simple test, does not imply necessarily, that I would get no sound drop-outs, if I was running a complex audio project in real-time.

I have tested, whether this external USB recording tool, works with my Samsung Galaxy Tab S Tablet, using a ‘StarTech.com’ OTG adapter. The results were resoundingly affirmative.

In This Earlier Posting, I had tested the same USB Sound Card, with my Samsung Galaxy S6 Smart-Phone. At that time, an attempt also to use it with my Tab S tablet had failed. In order to get the Scarlett 2i2 to work with the Tab S, the following two conditions need to be fulfilled:

The amount of current that the USB Slave Device may draw, needs to be reinforced, in principle, with a self-powered OTG adapter, or with a similar arrangement. The ‘StarTech.com’ is Not a self-powered OTG adapter, and with it, the Scarlett 2i2 is bound to draw too much current, for the likes of the Tab S. It was after all meant as an audio workstation workhorse, and not as a replacement for a simple USB Microphone.

The Master / Host Device, the Tab S, needs to have the correct drivers.

Condition (1) is something I was able to fulfill for now, in a roundabout way. I bought a ‘j5create USB 3.0 4-Ports Mini HUB’, with the part number ‘JUH340′. This is a self-powered hub by default, with its own power cord, and has Type A USB connectors up-stream and down-stream. Granted, it has a special up-stream cable, that connects to the hub with a special connector, just so that the user does not get this socket confused with the down-stream sockets. But then, the far side of that cable has a standard Type A USB jack.

This USB jack can be plugged, into the far side of the OTG adapter. Since the hub is self-powered, the current requirements of the Scarlett 2i2 are met by it, and not by the OTG adapter, and thus not by the micro-USB port on the Tab S, the latter of which now faces a minimum current load.

I have tested, whether this external USB recording tool, works with my Samsung Galaxy S6 Smart-Phone, using an ‘StarTech.com’ OTG adapter. The results were mixed. In An Earlier Posting, I had tested whether this external USB Sound Card, works under Linux. And the answer to that question was a resounding Yes.

When we plug an OTG adapter into a smart-phone or tablet, this puts the mobile device into Master / Host Mode, that would otherwise normally work in Slave Mode. Thus, we can then plug in a USB storage device, and hopefully have that recognized, while by default, we can only plug our mobile device into a computer, and have the computer recognize this mobile device, as the storage device.

But it is also plausible to connect other external devices to our mobile device, when using an OTG adapter. All this happens because the OTG adapter itself contains an additional chip, that gives it the ability to act as a USB Host. Whether such external devices will work or not, generally depends on two factors:

Whether the micro-USB port on the mobile device can output enough current, to supply the external / Slave device, and

Whether the mobile device possesses the drivers needed, for the USB device in question. Under Linux, this last question is more likely to be answered in the affirmative.

The OTG adapter I was using, uses its micro-USB side as the only power-supply. This means that if the connected device draws a full 500mA of supply current, we are pushing the limit, that is generally set for USB 2.0 PC ports.

One of the recent developments in Computing is, that the actual PCs and laptops have relatively poor sound-chip-sets inside, but that we can add an external sound card via USB. I refer to these as ‘USB Sound Cards’, but think that most people just refer to them as ‘USB Sound Devices’. An actual sound card, used to refer to a PCIe interface card, which we could physically insert into our PC bus, inside the case.

When people buy a USB microphone, because the USB connection is digital, they are in fact buying the Analog / Digital converter inside that microphone, which also makes it the logical equivalent to a sound card. And the fact that it would be a USB mike, does not imply worse quality than an external sound card. To the contrary, users can expect their USB mikes to outperform the internal sound on their devices, which is the whole point in buying them.

I have embarked on yet another project, which is to buy an external sound card that is physically separated from any actual mike or sound source, and to buy a quality mike as well. Hence, I have received my USB sound device already, that has 2 output channels and 2 input channels.

Mine is a “Focusrite Scarlett 2i2” USB Sound Device, even though I usually try not to make endorsements or indictments of commercial products. It is stated to be capable of sampling at 48 and 96 kHz, and stated to be capable of 24-bit precision. It requires a USB 2 connection.

Because sound is taken very seriously with such devices, its only available inputs are a combined XLR / TRS jack each (not a 3.5mm mini-cable). This means that I am still waiting for my XLR-jack microphone to arrive, without which I cannot test the Focusrite. ( :1 )

A plausible question which some readers might ask would be, Why did Dirk not just buy a USB mike? And my answer would be, Because what I pictured wanting was closer to a USB Sound Card, hence an Analog / Digital converter, that can accept a variety of input devices.

But this would also be the context, in which it might make sense to switch my laptop ‘Klystron’ into JACK sound-mode, which supports real-time 48 kHz at 24 bits, and which also supports 96 kHz…

After all, not long ago I was pondering what the settings should be, with which JACK will start, in terms of sample-rate etc..

A key point of this project is again, to test whether the device will work properly under Linux. ( :2 )